Power metal oxide semiconductor field-effect transistor (MOSFET) includes Vertical Double-Diffused MOSFET (VDMOSFET), and Lateral Double-Diffused MOSFET (LDMOS MOSFET), etc. Comparing with VDMOSFET, LDMOSFET has a plurality of advantages, such as better thermal stability and frequency stability, higher gain and durability, lower feedback capacitance and thermal resistivity, and constant input impedance and simpler bias circuit, etc.
FIG. 1 illustrates an existing N-type LDMOSFET. As shown in FIG. 1, the LDMOSFET includes a semiconductor substrate (not labeled) and a P-well 100 in the semiconductor substrate; an N-type drift region 101 in the P-well 100; a shallow trench isolation (STI) structure 104 in the N-type drift region 101 configured to increase the conductive path of the LDMOSFET so as to increase the breakdown voltage of the LDMOSFET; a P-type body region 106 in the P-well 100 at one side of the N-type drift region 101; and a gate structure 105 over on the semiconductor substrate. The gate structure 105 is over the P-type body region 106 and the N-type drift region 101; and a portion of the gate structure 105 may be over the STI structure 104. The gate structure 105 includes a gate dielectric layer (not labeled) on the surface of the semiconductor substrate; a gate electrode (not labeled) on the gate dielectric layer; and sidewall spacers (not labeled) on side surfaces of the gate electrode and the gate dielectric layer. Further, the LDMOSFET also includes a source region 102 in the P-type body region 106 at one side of the gate structure 105 and a drain region 103 in the N-type drift region 101 at the other side of the gate structure 105. The source region 102 and the drain region 103 are N-type doped.
However, in order to increase the breakdown voltage of such LDMOSFET, the size of the STI structure 104 needs to be increased to enlarge the conductive path. Thus, the STI structure 104 may consume a relatively large surface area of the substrate; and the production cost may be increased. In addition, the performance of the LDMOSFET may need further improvement. The disclosed device structures and methods are directed to solve one or more problems set forth above and other problems.